Geology Ch 18
Terms
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- important Quaternary mineral resources
- gold placers, sand, gravel, and borax
- the three interglacial stages
- Sanamon, Yarmouth, and Aftonian; named for localities of well-exposed interglacial soil and other deposits
- phenomenon in which the crust sinks and then rises as a result of loading by glaciers followed by melting
- isostasy
- mineral resources of the Quaternary are mainly
- sand and gravel along with some evaporite minerals such as borax
- cool period from about 1500 to the mid- to late- 1800s is known as
- Little Ice Age
- North American glacial stages
- Wisconsin, Illinoian, Kansan, and Nebraskan; named for the states representing the farthest advace where deposits are well exposed
- glacial stage
- time of extensive glaciation. at least four of these are recognized in North America, and six or seven are recognized in Europe
- were also affected by widespread glaciation
- other Northern Hemisphere continents
- how many warm-cold Pleistocene climatic cycles are recognized
- 20 warm-cold Pleistocene climatic cycles
- unsorted sediment directly deposited by a glacier is
- till
- Quaternary Period
- term for a geologic period or system comprising all geologic time or rocks fro the end of the Tertiary to the present; consists of two epochs or series, the Pleistocene and the Recent (Holocene)
- how many years ago did the Pleistocene Epoch begin
- 1.6 million
- how did glaciation occur in North America
- several intervals of widespread glaciation, separated by interglacial periods
- short-term climatic events can be explained by
- variation in solar evergy and volcanic reputions
- pluvial lake
- any lake that formed beyond the areas directly affected by glaciation during the Pleistocene as a result of increased precipitation and lower evaporation rates, e.g., Lake Bonneville
- changing positions of tectonic plates cause changes in
- oceanic and atmospheric circulation patterns
- formation of land bridges such as the one across the Bering Straits or between Europe and England during the Pleistocene resulted from
- a drop in sea level
- Holocene Epoch
- last of two epochs comrising the Quarternary Period. began 10,000 years ago
- Quarternary Period consists of two unequal epochs:
- the Pleistocene Epoch, from 1.6 million years ago to 10,000 years ago, and the Holocene Epoch, from 10,000 years ago to the present
- when the glaciers disapperared
- isostatic rebound began and still continues in some areas
- how are the Pleistocene climatic cycles recognized
- from paleontologic and oxygen isotope data derived from deep-sea cores
- in addition to glaciation, the Pleistocene is known for
- volcanism, folding, faulting, and uplift
- areas far beyond the ice were affected by Pleistocene glaciation:
- climate belts were compressed toward the equator, large pluvial lakes existed in what are now arid regions, and sea level was as much as 130 m lower than at presetn
- during the Pleistocene most of the world was what compared to today
- drier
- lakes that formed far from glaciers during times of glaciation in what are now dry areas are known as
- pluvial
- parameters Milankovitch used to explain the glacial-interglacial episodes of the Pleistocene
- the degree to which the orbit departs from a perfect circle; the angle a line perpendicular to the plane of the ecliptic; the precession of the equinoxes
- isostasy
- theoretical concept of the Earth's crust "floating" on a dense underlying layer; areas of less dense continental crust rise topographically above more dense oceanic crust
- during the Pleistocene Epoch, glacier covered about
- 30% of the land surface
- reason for short-term climatic changes, such as the Little Ice Age are
- not understood
- most recent ice age occurred during
- Pleistocene Epoch
- theory widely accepted as the explanation for glacial-interglacial intervals
- Milankovitch
- in addition to glaciation, the Pleistocene was also a time of tectonic unrest during which what was common
- folding, faulting, uplifts, and volcanism
- Little Ice Age
- interval of nearly four centuries (1300 A.D. to the mid- to late 1800s) during which glaciers expanded to their greatest historic extents
- Milankovitch theory
- explains cyclic variations in climate as a consequence of irregularities in the Earth's rotation and orbit
- pollen analysis can reveal past
- vegetation, climate
- two proposed causes for short-term climatic changes are
- changes in the amount of solar energy recieved by the Earth and volcanism
- proglacial lake
- lake formed by melt-water accumulating along the margins of a glacier
- pollen analysis
- identification and statistical analysis of pollen from sedimentary rocks; such analyses provide information about ancient floras and climates
- can be used to detremine oceanic surface temperatures during the Pleistocene
- O18 to O16 isotope ratios; identification of planktonic foraminiferal species; coiling ratios of planktonic foraminiferal species; and ocean chemistry
- Pleistocene Epoch
- first of two epochs comprosing the Quaternary Period. commonly called the Ice Age. occrred between 1.6 million and 10,000 years ago
- loading of the Earth's crust by Pleistocene glaciers caused
- isostatic subsidence
- interglacial stage
- time between glacial stages when glaciers cover much less area and global temperatures are warmer than during a glacial stage
- probably occur as a consequence of the changing positions of tectonic plates
- major glacial intervals separated by tens or hundreds of millions of years